1. Field of the Invention
The present invention relates to a sheet feeding apparatus for feeding a copying machine, a facsimile machine, a printer or the like with originals or recording sheets and relates to an image forming apparatus using the same.
2. Description of Related Art
In recent years, in the field of sheet feeding apparatuses equipped in image forming apparatuses such as copying machines and printers, reduction of operation noise as well as stabilization of sheet feeding performance has been a challenge that has been receiving attention.
The sheet feeding apparatus used in a copying machine, a printer or the like is adapted to separate and send out stacked sheets one after another. In a conventional method adopted in the sheet feeding apparatus, sheets are separated one by one by means of a feed roller for feeding a sheet and a separating pad that is biased against the feed roller to prevent double feeding. In this sheet separating method, stick-slip (minor vibration) may occur between the sheet and the separating pad depending on the type of the sheet fed, and this vibration sometimes causes an unusual noise (uncomfortable noise). To prevent such an unusual noise from occurring, in a method that has been proposed, for example in Japanese Patent Application Laid-Open No. H8-091608, a damping member is provided on the separating pad to suppress vibration of the separating pad, thereby preventing generation of an unusual noise.
However, although vibration of the separating pad can be effectively reduced by the above-described conventional method, it is not possible to sufficiently reduce vibration of the sheet itself, which is the source origin of the vibration.
Accordingly, there is a possibility that the vibration suppression effect cannot be achieved depending on the structure of the sheet feeding apparatus and that the vibration may be magnified to make the unusual noise lauder.
To suppress vibration of the sheet, contact pressure of the feed roller and the separating pad may be adjusted. However, when the contact pressure is made small, sufficient sheet feeding performance cannot be achieved, and sheet feed failure may occur. In contrast, when the contact pressure is made large, the possibility of occurrence of stick-slip between the sheet and the separating pad increases to make the possibility of generating an unusual noise higher.